Distal-type cervical spondylotic amyotrophy - Assessment of pathophysiology from radiological findings on magnetic resonance Imaging and epidurally recorded spinal cord responses

Study Design. Six cases with distal-type cervical spondylotic amyotrophy are reported. Objective. To investigate the pathophysiology of distal-type cervical spondylotic amyotrophy from magnetic resonance imaging and intraoperative evoked spinal cord responses. Summary of Background Data. Cervical spondylotic amyotrophy had a characteristic clinical symptom of severe muscular atrophy with no or insignificant sensory deficit. Selective ventral root lesions or intrinsic spinal cord lesions have been proposed as the pathophysiology of cervical spondylotic amyotrophy, but they have not been well understood. Method. Six patients with distal-type cervical spondylotic amyotrophy were described, and their magnetic resonance imaging and evoked spinal cord potentials after median nerve, motor cortex, and spinal cord stimulation were investigated. Results. Sagittal T2-weighted magnetic resonance imaging showed high signal intensity change within the spinal cord at C4-C5, C5-C6, and C6-C7. All patients underwent laminoplasty. The attenuation of postsynaptic potentials with preserved presynaptic potentials at C4-C5, C5-C6, and C6-C7 was characteristic in the evoked spinal cord potentials after median nerve stimulation. The amplitude of the evoked spinal cord potentials after median nerve stimulation was preserved at C2-C3. This means that lateral posterior column in the spinal cord had less or no involvement in distal-type cervical spondylotic amyotrophy. Concomitant hyperactivity of the patellar tendon reflex was correlated with the abnormality in the evoked spinal cord potentials after transcranial electric stimulation. Conclusions. The results suggest a longitudinal gray matter lesion as one pathophysiologic feature, and that less damage to the lateral posterior column is the reason for the preservation of sensory function in the patients with distal-type cervical spondylotic amyotrophy described in this study.